Photosensitive composition comprising light-sensitive polymer

ABSTRACT

This invention is concerned with a photosensitive composition having, as a pendant, Alpha -phenyl cinnamylidene acetyl group of the generic formula:

United States Patent 1 T Tanaka et al.

[ 1 Oct. 23, 1973 [75] Inventors: llideaki Tanaka, Hiratsuka; MinoruTsuda, Kanagawa, both of Japan [73] Assignee: Agency of IndustrialScience &

Technology, Tokyo, Japan 22 Filed: Nov. 11,1971

21 Appl. No.: 197,755

[30] Foreign Application Priority Data Nov. 14, 1970 Japan 45/99826 [52]U.S. Cl. 96/115 R, 96/35.], 204/l59.l4 [51] Int. Cl. G03c 1/68 [58]Field of Search 96/115 R, 35.1; 204/159.l4

[56] References Cited UNITED STATES PATENTS 3,257,664 6/1966 Leubner eta] 96/115 R 3,635,720 1/1972 Stcppan etal. ..9e/11s.9

Primary ExaminerRonald H. Smith Attorneyl(urt Kelman [57] ABSTRACT Thisinvention is concerned with a photosensitive composition having, as apendant, a-phenyl cinnamylidene acetyl group of the generic formula:

1 Claim, 4 Drawing Figures .1 i Pl-IOTOSENSITIVE COMPOSITION COMPRISINGLIGHT-SENSITIVE POLYMER This invention relates to a novel photosensitivecomposition. I v Poly(vinyl cinnamate) has been known to form anexcellent photosensitive resin and is now used extensively in printing,in manufacture of integrated circuits, etc. The ultraviolet absorptionspectrum of poly(vinyl cinnamate) has itsabsorption peak at 275 mu.Thus, this polymer does not absorb rays of wavelengths exceeding 340Addition of a sensitizer is required, therefore, where the poly(vinylcinnamate) resin is desired to be rendered sensitive to rays ofnear-ultraviolet wavelengths. Even when the sensitizer is added, theresin fails to provide very satisfactory photo sensitivity to rayshaving wavelengths exceeding 400 mu. Nevertheless, poly(vinyl cinnamate)is used extensively in many fields because of its superiority in thermalstability, storageability, etc. i

As one of the photosensitive resins sensitive to longer wavelengths,there has heretofore been known poly(vinyl cinnamylidene'acetate)(hereinafter abbreviated as PVCA) (U.S. Pat.-No. 3 ,257,664). PVCA, uponincorporation therein of a sensitizer, acquires improvedphotosensitivity even in the wavelength zone of visible rays but suffersfrom very inferior thermal stability and storageability. When such PVCAis put to storage for a long time, it gradually undergoes gelation andeventually becomes unusable. If it is held at a temperature higher thannormal room temperature, then it rapidly induces cross-linking reactionand is converted into a gel. Despite a higher photosensitivity than thatof poly(vinyl cinnamate), PVCA finds a rather restricted field of usesbecause it is difficult to handle.

It is the main object of this invention of provide a photosensitivecomposition highly sensitive to visible rays and stable thermally. Sincethe photosensitive composition according to the present invention hassufficient sensitivity also to visible rays, it does not require the useof an expensive optical system incorporating a xenon lamp', mercurybulb, or quartz lens for the purpose of exposure. Satisfactory exposurecan be accomplished byan optical system using a tungsten lamp as thelight source. Further, the present photosensitive composition enablesthe exposure to be made by means of projection which permits a givenimage to be enlarged or contracted as desired. In the manufacture ofintegrated circuits, for example, the image of a desired circuit can beprojected on this resin without damaging the mask. Thus, handling can bemade easier and more economical. v

FIG. 1 shows the spectrograms obtained for poly(vinyl cinnamate)sensitized by 1,2-benzanthraquinone and 9,10-phenanthroquinonerespectively, v

7 FIG. 1 show s the spctrograms obtained for the photosensitivecomposition of the present invention sensitized by 1,2-benzanthraquinoneand 9,10-phenanthro: quinone respectively. 7 v rhiiiviii'di's'irimencedstudies with a view to improving the thermal stability andstorageability of PVCA mentioned above. In the course of their studies,they foresaw possibility of PVCA by attaching a phenyl group to thealpha position of the photosensitive group cinnamylidene acetyl therebyallowing the photosensitive group to acquire the diphenyl butadieneconfiguration. Contrary to what was expected, this diphenyl butadienecarboxylic acid (at-phenyl cinnamylidene acetic acid) did not induce anyphotodimerization of molecules at all, while cinnamylidene'acetic acidwas found to be photodimerizable. For the purpose of obtaining aphotosensitive resin having satisfactory thermal stability, theinventors made attempts to convert this diphenyl butadiene carboxylicacid, a substance totally destitute of photosensitivity, into aphotosensitive resin; Fortunately, a high molecular compoundpolyvinyl-a-phenyl cinnamylidene acetate (hereinafter abbreviated asPVaPhCA) was able to be synthesized by having diphenyl butadienecarboxylic acid bonded to the main chain of polymer and the resultantcompound was found to be a photosensitive composition havingsubstantially the same degree of sensitivity as PVCA and much higherdegree of thermal stability than PVCA.

When PVCA was heated at about C for about one hour, it became unusuablebecause more than 20% Brit; photosensitive group was decomposed andconsequently cross-linked. By contrast, PVaPhCA of the present inventionremained virtually unaffected under the same conditions. When thispolymer was finely divided into a powdery state and then exposed in theair for more than one year, it also remained virtually unaltered. Whenthe phenyl group was attached to the alpha position of cinnamylideneacetyl, the polymer showed thermal stability higher than that of thepolymer having some other group, such as alkyl group or cyano group,attached to the said position. This may logically be explained bypostulating that the diphenyl butadiene configuration provided thedesired stability as expected.

The photosensitive high molecular compound having a-phenyl cinnamylideneacetyl as its photosensitive group can be produced by esterifying a highmolecular polyvinyl alcohol type polymer with a-phenyl cinnamylideneacetate. Consequently, there is obtained a polymer of the followingstructural formula:

(wherein, R denotes a high molecular vinyl alcohol type polymer).

PVaPhCA thus obtained has the peak of its ultravio let absorptionspectrum at 333 my, a value substantially the same as that of the peakof diphenyl butadiene, and can absorb rays of wavelengths up to about440 mu. This means that this compound has a photosensitivity wavelenghtzone up to 440 mp. without requiring the incorporation of anysensitizer. This sensitive wavelength zone is substantially equivalentto the wavelength zone enjoyed by poly(vinyl cinnamate) using asensitizer.

PVaPhCA may have its photosensitivity further enhanced by incorporatinga sensitizer. For this purpose, the sensitizers which are used forenhancing the photosensitivity of poly(vinyl cinnamate) are invariablyavailable. The incorporation of such sensitizer has a greater effect inthis compound than in poly(vinyl cinnamate).

S-Nitroacenaphthene enhances the sensitivity of poly(vinyl cinnamate) to440 my. and that of PVaPhCA to about 480 mp.. 1,Z-Benzanthraquinoneincreases the sensitivity of poly(vinyl cinnamate) to 430 mp. and thatof PVaPhCA to 500 mp. The sensitivity of PVaPhCA can be enhanced up toabout 560 mp. by such xanthene dyes as eosine, erythrosine, and rosebengal. These coloring matters enhance the sensitivity of PVaPhCA tovisible rays. Consequently, PVaPhCA with enhanced sensitivity enablesthe exposure by enlarged projection to be effected with a tungsten lamp.In the manufacture of integrated circuits, it is strongly desired toincrease the sensitivity enough to respond to rays of mercury lamphaving a wavelength of 436 mp. but not so much as to respnd to visiblerays having wavelengths exceeding 500 mp.. This object is attained byusing PVaPhCA suitably incorporating such sensitizer. PVaPhCA not onlyenjoys excellent thermal stability but also possesses highphotosensitivity. Moreover, the zone of photosensitive wavelengths canbe freely regulated over the near-ultraviolet band through the visibleband. Thus, PVaPhCA is expected to find a wide range of uses.

Now, preferred embodiments of this invention are described. They arecited for the purpose of illustration and should not be construed aslimiting the present invention in any way.

EXAMPLE 1 With 40 ml of triethylamine and 80 ml of acetic anhydride,52.9 g of cinnamaldehyde and 55 g of phenylacetic acid were heated at130 C for about hours to afford 84 g of a-phenyl cinnamylidene aceticacid (yield 84 percent). a-Phenyl cinnamylidene acetyl chloride wasproduced by agitating '15 g of this phenyl cinnamylidene acetic acid, mlof thionyl chloride and 15 ml of toluene at 70 C for 1 hour and,subsequent to the ensuing reaction, removing excess thionyl chloride bydistillation. This chloride was combined with 2.6 g of polyvinyl alcoholand 50 ml of pyridine and agitated at 50 C for about 5 hours. Oncompletion of the reaction, the reaction system was placed in a largevolume of alcohol, with the result that there was produced a brownpolymer. This polymer was dissolved in cychohexanone to form aphotosensitive liquid. This photosensitive liquid was spread on adry-plate glass and dried, and exposed through Kodak Step Table No. 2 toa superhigh-pressure mercury lamp (Model SI-IL-lO- OUV made by Toshiba)placed at a distance of 25 cm. The sensitivity was equal to thatproduced by poly(vinyl cinnamate) which was sensitized with 5-nitroacenaphthene or N acetyl-fl-nitro-l naphthylamine.

The sensitivity of the polymer was measured spectroscopically by using axenon lamp as the light source. The results indicate that thesensitivity ranged in wavelength between 200 my and 450 my. and that themaximum sensitivity existed around 350 my.

EXAMPLE 2 Fifteen g of a-phenyl cinnamylidene acetyl chloride wasdissolved in 70 ml of methylethyl ketone and kept at about 5 C. With theaqueous solution of polyvinyl alcohol (2.6g/50ml), 8g/50ml of sodiumhydroxide and 70 ml of methylethyl ketone were mixed. The mixture wascombined with theacid chloride solution prepared in advance and thenagitated at 5 C for about 90 minutes. Thereafter, the reaction solutionwas allowed to stand at normal room temperature. The polymer formed inthe upper layer was dissolved in cyclohexanone to form a photosensitiveliquid.

The results of the sensitivity measurement indicate that this polymershowed essentially the same degree of sensitivity as that of the polymerof Example I.

EXAMPLE 3 TABLE 1 Photosensitive wavelength zone 200 my. to 480 my.

Name of sensitizer S-Nitroacenaphthene Eosine 200 my. to 560 mp.Erythrosin Do. Rose bengal 200 mp. to 600 mp.

Thio-Michlers ketone 200 my. to 620 my.

EXAMPLE 4 Photosensitive liquids were prepared by adding 1,2benzanthraquinone and 9,1 O-phenanthroquinone, each in an amount of 5percent based on the weight of polymer, to 2.5 percent cyclohexanonesolutions of poly(vinyl cinnamate) and PVaPhCA. The photosensitiveliquids were spread on quartz glass plates, dried, and thereaftermeansured for sensitivity spectroscopically by means of a spectroscopicsensitivity tester provided with a 2-KW xenone lamp and a spectroscope.The development was effected by submerging the film for two minutes inmethylethyl ketone in the poly(vinyl cinnamate) and in tetrahydrofuranin the case of PVaPhCA respectively.

The results are shown in FIG. 1 wherein FIG. 1 (A) and FIG. 1 (B) showthe spectrographs for cyclohexanone solution of poly(vinyl cinnamate)sensitized by 1,2-benzanthraquinone and 9,l0:p henanthroquinone"interest from FIG. 1 that PVdPhCA films sensitized with the sensitizerswere conspicuously sensitive in the range of 400 my. to 500 mu. Thesefilms lacked photosensitivity at wavelengths beyond 500 my. and,therefore, could be handled safely under rays from a yellow darkroomlamp. The films of poly(vinyl cinnamate) has very weak sensitivitybeyond 400 my Thus, they could not practically be used in wavelengthsbeyond this level. Example 5:

PVaPhCA, PVCA, poly(vinyl a-methylcinnamylidene acetate) and poly (vinylcinnamate) each prepared in the form of 2.5 percent cyclohexanonesolution were spread on quartz glass plates and then dried at roomtemperature under a reduced pressure to form test films. The test filmswere kept in an oven at C for 1 hour. Ultraviolet absorption spectrawere obtained of these films before and after the heating in the 6 oven,to compute the ratio of thermal reaction of their dant, a-phenylcinnamylidene acetyl group of the gephotosensitive groups. The resultsare shown below. neric f l Photosensi- PV a-methyl Poly(vinyl- PVaPhCAPVCA tive cinnamylidene cinnamate) 5 resin acetate CH=CH CH=C C Q Ratioof g thermal l% 23% 40% 1% decomposition What is claimed is: l. Aphotosensitive composition comprising a photosensitive vinyl alcoholtype polymer having, as its pen-

